FYI - this test was not bad until the physitrist (?) got to my right leg. He keep saying stop moving your leg, I wasn't moving it at all. He keep manipulating my leg and foot with different electrical strengths, until finally he turned the machine wide open felt like it burn my leg to the bone inside and finally my leg moved. This was excruciatingly painful...I believe the tech went above and beyond the norm to get the readings he wanted. My leg hurt for 3 days, and my thumb (he did the same) hurt so bad I could hardly use it for a week.
Electromyography studies the electrical impulses in your muscles. It's used to diagnose neurological and neuromuscular conditions and disorders. NCV stands for nerve conduction studies, which does the same thing, except it tests the nerves in your extremities.
Electrodes are attached to your skin and tested through stimulation of the muscle fibers and/or the nerves.
It's not painful.